How to get the SPL of a signal?
This seems to work to get the overall dB SPL level for the signal, using peak voltage as AI. My question is, how can I apply this to an FFT of the input signal, to get the intensity level per frequency?
How to plot the frequency response in MATLAB?
Using Matlab, plot the frequency response (magnitude vs. frequency, and phase vs. frequency) with frequency on a log scale (frequency range: 10^-1 ~ 10^2).
What happens when Pref data varies with frequency?
If your Pref calibration data varies with frequency (e.g. microphone with non-flat frequency response) then it’s a little more complicated than the above, but the same basic principles apply. Note also that if you want weighted dB SPL (e.g.
Which is the range on a frequency response graph?
The frequency range respresented on this graph is 20Hz to 20,000Hz (20kHz), which is the range of typical human hearing. By looking at this frequency response graph, we can see how capable the speaker is at reproducing the frequencies we can hear. Generally, the range of bass frequencies encompasses 20Hz-500Hz.
How to calculate the FFT of a microphone signal?
Here is some python code to demonstrate what I have thus far, my goal is to apply this to ultrasonic signals that contain many different frequency components.
What is the FFT to Spectrum in Decibel?
Here is a 10 seconds-long 440hz sine wave normalized at 0 dBFS. When computing the STFT (with the code below) of this audio file, I noticed that max (abs (STFT)) is around 248.33. (more generally, it seems to be approximately fftsize/4 for this particular file).
Where are the signal values on a microphone?
The output of a microphone is a voltage level that corresponds to the pressure on the membrane. The part that confuses me is why are the output signal values located above and below the average (picture attached). Do the values “above and below” correspond to the membrane deflecting, and then going back to its original position?